Your comments are very rational and to the point. I shoot birds and tend to crop most of the time. Thus increased MPs helps. This is the big advantage of the crop sensor-longer reach. Measuring IQ at ISO 100 the SNR will go down as MPs increase but resolution goes up. If one needs resolution then more MPs really helps or get a longer reach lens or decrease camera/subject distance. Increased MPs and shooting at ridiculously high ISO will degrade the SNR to unacceptable levels. Those of us who welcome the higher MPS can tolerate the undetectable (by the eye) increase in noise at ISO 100. So if you want low noise at high ISO get larger sensels-period.
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A bird in the viewfinder is worth...